In almost all electric or electronic devices, manual operation is effected by switches. These switches are almost always designed mechanically, two metal parts being brought into contact or respectively out of contact in order to close or respectively to open a circuit. However, this mechanical design has the disadvantage, amongst others, that it has mechanical wearing parts and consequently only has a limited service life and is fundamentally water-sensitive, such that, where required, a costly casing is necessary.
Optical switches are already known; however, up to now they have been extremely lavish and, consequently, expensive and do not yet have the required standard of operational reliability. However, in principle, optical switches have advantages, as they manage, generally speaking, without any moving mechanical parts and the switching process can be triggered by mere tapping or by contacting a control surface or by simply through approximation to a sensor.
Furthermore, so-called proximity sensors or also rain sensors are known in the technology, by means of which the displacement of an object onto a surface or the contacting or wetting of a surface can be detected, devices being known in these cases which output a signal containing data regarding the direction of displacement and the speed of displacement of the object. Such a device is known, for example, in WO 95/01561.